Paper drive



March 28, 1961 F. F. OFFNER PAPER DRIVE Filed July 15, 1957 INVENTOR B am/(Lin F 0 fr/er 3PM, Jbfilfifb. & 1

ATTORNEYS This application relates to a paper feed mechanism for recording devices such as direct-writing oscillographs and the like and more particularly to an improved construction and arrangement for cooperating drive and counterpressure rolls between which the continuous paper'strip or web is drawn from a supply roll in order to ensure a straight and true travel of the strip through the rolls and past the recording elements.

In the past it has proven most diflicultto produce a paper feed mechanism which will feed the paper straight and true without using exceptional care to insure a very high degree of precision in both the feed mechanism and in the paper itself. An object of the present invention is to eliminate the need for unusually high precision in both the mechanism and the paper.

The conventional drive roll component consists of a single drive roll and a counter-pressure roll each as long as the width of the paper strip itself. To ensure that the example its diameter at" the near end' is" exactly l jin'ch while its diameter at the far end is 1.002 inches, then-for everyinch the nea'redge of the paper travels" forward,- the far edge of the paper will travel 1.002 inches After the paper has traveled 100 inches'there' will be a total' of 0.2

inch difference in travel 'betw'een the two edges of the t paper. This is on the assumption that therolls are tightly enough in contact to prevent-any slippage of thepaper. This difference in amount ofpaper travel will result in the paper not running flat and'true from the sup'ply roll to andthrough the feed rolls but rather will create slack atthe far edge and possibly skewing of the paper travel. The development of slackin" the paper will resultl in a difference of tension at the two edges? This differential tension effect is utilized to advantage the presentinvention in maintaining the travel of the" paper straight and true. V V v" a In particular, in accordance with the present invention the drive roll is divided axially into a pluralityof roll sectionsrnounted upon a' rotatable shaft. 1 The'ro1l sec tions are held under axial compression between friction discs also mounted upon the shaft. The roll sections will rotate together provided all'areexactly the same diameter but they are enabled to turn relative to one another about' the shaft axis if there is a-suflicient difference in force tending to turn them. 7

'If one assumes that because ofmanufacturing tolerances the roll sections at the far edge of the paperstrip are slightly larger in diameter than those at the near edge, and hence that the far edge of the paper is pulled faster than the near edge, as soonasappreciable slack develops by. 'Allen 'screW 24 and servesato drivev the-.shaftd'l-iin 2,977,112 Patented Mar. 28, 1961 at the far edge, the pulling tension is all transferred to the near edge. However, the roll sections pulling the near edge will not have enough tension to pull the paper without slipping on the shaft and consequently will slip until the slack at the far edge is used up and equal tension is developed across the width of the drive roll assembly and paper thus permitting all rolls to pull together.

One practical embodiment of the invention will now be described in detail and is illustrated in the accompanying drawings wherein;

Fig. 1 is a view in side elevation showing in principle a typical paper feed mechanism;

Fig. 2 is a longitudinal view partly in elevation and partly in section of the improved drive roll construction together with the counter-pressure roll;

Fig. 3 is a transverse vertical section on line 3 3 of Fig. 2; and

Fig. 4 is a transverse vertical section on line 4-4 of Fig. 2.

With reference now to the drawings it will be seen that the improved paper drive comprises a supply roll 10 of paper 11, the paper roll being mounted for rotation on a shaftlZ, the opposite ends of which are received in pedestal bearings 13 secured to a supporting surface 14. A tension member in the form of a convex spring leaf 15 has one end thereof'secured in place on the supporting surface 14 and the opposite end bears against the paper roll 10 to hold back'on the roll and hence produce tension in the paper strip 11 being pulled from it. I

As shown in Fig.2 in particular, the :drive- 'or' feed. roll R is comprised of aplurality of individual roll. sections16 made of a rigid material suchas steel or'th'elikeand mounted in generally sideby-side relation along the length of a supporting shaft17 that has a fiat 17a that-extends for the full length of the shaft. Shaft 17 is parallel with shaft 12 and is supported :at itsopposit'e ends in pedestal bearings 18". As is clearfroniFig. 4, the central openings 16a in the roll sections 16 have a circularconfiguration so as to enable them:tti'slipindividually and relative to one another about the axisiof shaft 17. If desired, the surfaces of the roll sections 16 may. ,be

knurledas at ldbso as to establish abetter grip 'on'fthe paper, .7 4 The roll sections 16 are separated from each .otherf'by friction discs "18 *likewise made of afrigid'material such as steel, the discs. .18 being mounted on shaft 17 and the central openings 18a in the discs being iD-shaped and-conforming to the peripheral configuration-0f; shaft .17 thus keying the discs to the shaft and preventing any-rotation of thediscs on theshaft.

The assembly of'r'oll'sections 16 alt'ernating' with-the friction 615C518. is :held in axial compression on shaft '17 by any suitable-means. In thezpresent embodiment, a

collar19' is=fastenedonto onefendfof shaft-17 by an Allen 'pression: force exerted on theassemblyzofroll sections 16 and separating friction discs 18 bywaslierr21 is adjusted to the point 'where the torque,- developedby all of the roll sections 16 pulling togetheron the paper stripll is more than sufiicient to pull thepaper against thecounter tension produced on the paper roll 10 byxthe-loading spring 15. Theaxial compression. exerted by thrust washer 21 shall not, however, b'esuflicient to permit only one or, a few of the rollsectionsplfito pull lhe paper-. 1. A bevelled gear 23 is .securedto'onei end; of shaftalfl rotation, the gear 23 being meshed with a gear transmission driven by any suitable means such as an electric motor. The motor and gear transmission have not been illustrated since they are not essential to the inventive concept hereinafter claimed.

The counter-pressure roll R1 can be a single roll but preferably is also divided axially into a plurality of roll sections mounted for free rotation on a shaft 25 arranged parallel to and above shaft 17. Each roll section of the counter-pressure roller is preferably constituted by an inner cylindrical portion 26 of rigid material such as steel and which is covered by a rubber sleeve 27. Such construction eliminates the need for the paper 11 to be able to slip under the pressure roll, in order to equalize tension.

Opposite ends of the counter-pressure roll supporting shaft 25 are received in arms 28, the opposite ends of these arms being articulated at 29 to supports 30 secured to the supporting surface 14. A helical spring 31 in tension is secured between the supporting surface 14 and each arm 28 intermediate the'ends of the latter thereby to cause the counter-pressure roll assembly R1 to bear against the drive roll R with the paper strip 11' therebetween.

In the operation of the improved drive, shaft 17 is positively driven by power applied to gear 23. Rotation of shaft,17 causes positive rotation of the friction discs 1-8 and the latter bearing against the adjacent faces of the rolls 16 act as a slippable clutch for driving the rolls 16. Should now one edge of the paper strip 11, for example, the right edge as viewed in Fig. 2, be pulled between the drive and counter-pressure. rolls R, R1 faster than the left edge, and an appreciable slack develops at the left edge, the pulling tension is all transferred to the left edge. However, the roll sections 16 pulling the left edge will not have enough tension to pull the paper strip 11 without slipping on the shaft 17.. Consequently, the roll sections 16 at the left end will slip in rotation relative to the remaining roll sections until the slack in the left edge is used up and equal tension is developed across the width of the paper strip 11, thus permitting all roll sections 16 to again rotate with shaft 17 and pull together on the paper strip. The amount of slippage necessary to equalize the tension is negligible so far as average paper speed is concerned, but suflicient to maintain the drive of the paper straight and true.

In conclusion, it is understood that the illustrated embodiment of the invention is to be regarded as typical rather than limitative and hence can be departed from without, howevendeparting from the spirit and scope of the inventive concept as defined in the appended claims. Also, while the invention has been described and illustrated in its application to the feeding of a paper strip for recorders it is obvious that the same inventive principle can be utilized wherever anaccurate feeding or transport of a thin flexible sheet material is required.

I claim: V v

1. In a device for feeding a stripofthin'flexible material longitudinally of itself, a drive roll for pulling said strip under tension from a supply source and means for applying pressure between said strip and said drive roll, said drive roll being constituted by a plurality of coaxial roll"sections arranged along a line of contact extending transversely across substantially the entire width of said strip and being in simultaneous contact respectively with different surface portions of said strip along said contact line, and means including slippable driving means cooperative with said roll sections for driving said roll sections in an independent manner.

2. In a device for feeding a strip of thin flexible material longitudinally of itself, a drive roll for pulling said strip under tension from' a-source of supply, means applying pressure between said strip and said drive roll, said driveroll being constituted by a plurality of cosaid shaft in rotation, slippable clutching means .associaxial roll sections mounted on a rotatable shaft and turnable on said shaft with respect to each other, said roll sections being arranged along a line of contact extending transversely across substantially the entire width of said strip and being in simultaneous contact respectively with different surface portions of said strip along said contact line, means for driving said shaft in rotation, and slippable clutching means associated with each roll section transmitting the shaft rotation to said roll sections.

3. In a device for feeding a strip of thin flexible material longitudinally of itself,. a drive roll for pulling said strip under tension from a source of supply, means applying pressure between said strip and said drive roll, said drive roll being constituted by a plurality of coaxial roll sections mounted on a rotatable shaft and turnable on said shaft with respect to each other, said roll sections being arranged along a line of contact extending transversely across substantially the entire width of said strip and being in simultaneous contact respectively with different surface portions of said strip along said contact line, means for driving said shaft in rotation and slippable clutching means between adjacent roll sections transmit-ting the shaft rotation to said roll sections, said slippable clutching means being constituted by friction discs located on said shaft between and abutting adjacent faces of adjacent roll sections and being 'keyed to said shaft, and means maintaining said roll sections and friction discs in axial compression, said compression being so adjusted that the available torque from one roll section is insuflicient to transport said strip material Whereas the combined torque from all roll sections acting simultaneously is more than suflicient.

4. In a device for feeding a strip of thin flexible material longitudinallyof itself, the combination comprising a rotatable drive shaft, a plurality of roll sections mounted co-axially on said shaft and being turnable on said shaft with respect to each other, means applying pressure between said strip and said roll sections, said roll sections being arranged along a line of contact extending transversely across substantially the entire width of said strip and being in simultaneous contact respectively with different surface portions of said strip along said contact line, friction discs located on and keyed to said shaft between adjacent roll sections, and means maintaining said roll sections and friction discs in compression. v

5.;A device as defined in claim 4 for feeding'strip'material wherein said drive shaft includes a longitudinally extending flatand said friction discs have central openings corresponding to the peripheral configuration of said shaft thereby keyingv said discs to said shaft.

6'. In a device for feeding a strip of thin flexible ma terial longitudinally of itself, a drive roll for pulling said strip under tension from a source of supply, said drive roll being constituted by a plurality of co-axial ated with each drive roll section transmitting ithe shaft rotation to said drive roll sections and means for applying a pressure between said strip and saiddrive roll sections, said pressure means being constituted by a pressure roll comprising a plurality of co-axial pressure roll sections mounted for rotation parallel with said drive roll sections and spring means loading said'pressure roll sections into contact with. the face of said strip opposite said drive roll sections.

7. In a device for feeding a strip of thin flexible material longitudinally ofitself, a drive roll for pulling said strip under tension from a source of supply, said drive roll being constituted by a plurality of co-axial drive roll sections mounted on a rotatable shaft and arranged along a line of contact extending transversely across substantially the entire width of said strip and being in simultaneous contact respectively with different surface portions of said strip along said contact line, said drive roll sections being rotatable on said shaft and turnable with respect to each other, means for driving said shaft in rotation, slippable clutching means between adjacent drive roll sections transmitting the shaft rotation to said drive roll sections, said slippable clutching means being constituted by friction discs located on said shaft between and abutting adjacent faces of adjacent drive roll sections and being keyed to said shaft, means maintaining said drive roll sections and friction discs in axial compression, said compression being so adjusted that the available torque from one drive roll section is insufficient to transport said strip material whereas the combined torque from all drive roll sections acting simultaneously is more than sufiicient, and means for applying a pressure be tween said strip and said drive roll sections, said pressure means being constituted by a pressure roll comprising a plurality of co-axial pressure roll sections mounted for rotation parallel with said drive roll sections and spring means loading said pressure roll sections into contact with the face of said strip material opposite said drive roll sections.

References Cited in the file of this patent UNITED STATES PATENTS 

